HTML and CSS Reference
Hit F12 to open it. It's similar to Firebug for Firefox or
Developer Tools in Chrome , but it's not that powerful.
Inspect the header bar and go through the entire list
of elements that it contains and see from where is
the gap being added. The path would be:
#header - div.container - #logo - h3.incl - a
When you've reached the #logo h3.incl a , you may
have noticed that the gap isn't visible anymore.
Somewhere between the h3.incl and a element the
gap is added.
The easiest fix would be to set a height for h3.incl , as
you did with the a tag.